A trailer brake system of prior art types deals with the main concept of receiving a signal from the leading truck tractor for causing the deceleration of the command to the tractor brakes, which control the command to the pressure trailer brakes so that the drawn trailer will receive the same identical brake deceleration command as does the pulling truck tractor. The trailer brake system includes a control circuit which establishes the control rate of the trailer brake deceleration. Since an identical brake deceleration rate results in a constant braking distance of the tractor, an identical braking distance results in the trailer so that the same velocity is experienced by the tractor and the trailer. These results determine the control factors of the control circuit. Such a prior art trailer brake system is shown and disclosed in German Patent No. DE 27 52 641 A1. The tractor and trailer are appropriately connected together by a conventional coupler. When the brake is activated by means of air pressure supplied to the tractor brake, the trailer has the tendency to push into the tractor. As a consequence of the amount of pressure supplied to the trailer brake cylinders or by a modification of the intensity of the energy, the trailer brake system will assure that during such brake action the force which pushes against the tractor in the forward direction will be limited to a given predetermined value. This pushing force of the trailer brake system results in an increase in the deceleration signal. The goal of such control action is the equalization of the trailer brake system deceleration rate with that of the tractor. As soon as the trailer brake system reaches such a predetermined value, the trailer moves toward the forward direction of travel.
An overload warning, which is suitable for at least one trailer brake in such a brake system, is shown and disclosed in the International Patent Application No. WO 84/00406. This type of the state of the art is thus used as a pattern for new developments. With this state of technology, the measure for the load on the trailer brake is the temperature dependent developed in the vicinity of the brake drum or brake disc. By means of a temperature comparator, a warning circuit is normally activated at high temperatures to result in the actuation of optical and acoustic signals.
A disadvantage with this type of prior art operation is the sluggishness or undue delay in the temperature sensing. The resulting high temperature and the excessive load on the trailer brake can have a damaging effect before a warning is initiated, which is a consequence of the sluggishness.